Power distribution systems typically include circuit-interrupting devices, such as circuit breakers, sectionalizers, and reclosers provide protection for the power distribution systems and the various apparatus on those power distribution systems, such as transformers, reactors, and capacitor banks by isolating a faulted section from the main part of the system. A common problem in almost any electrical power distribution system is a momentary disruption of electrical service, such as might be caused by a momentary short circuit. A fault current in the system can occur under various conditions, including, for example, power lines strung between poles could swing under wind loading, momentarily touching each other or a grounded conductor, lightening, an animal or tree shorting the power lines, arcing, or other transitory events. Any of these events could cause momentary power line short circuits or current surges, which could burn out a fuse, trip a circuit breaker, or damage other equipment in the power distribution system.
Conventional circuit-interrupting devices sense a fault and interrupt the current path. Conventional reclosers also reclose the current path and monitor continued fault conditions, thereby re-energizing the utility or power transmission line upon termination of the fault. This provides maximum continuity of electrical service. If a fault is permanent, the recloser remains open after a certain number of reclosing operations that can be pre-set.
Power distribution single-phase line-to-ground temporary faults constitute majority of the faults on high voltage transmission lines. For example, at 500 kV lines in about 70%-85% of the cases, after tripping of a faulted phase at both sides of a transmission line, fault is self-extinguished. It takes typically one to two seconds for reliable self-deionization of a secondary arc, supported by electromagnetic and electrostatic influence of healthy phases, but sometimes an arc lasts significantly longer.
Currently, fixed time delays are employed after a fault to automatically reclose a transmission line. However, using fixed time delays for single-phase auto-reclosing has two disadvantages. First, if the delay is longer than the duration of the arc fault self-extinguishing time, stability of the power system may be adversely affected. Secondly, if the delay is shorter than the arc fault duration, reclosing will be unsuccessful. This may cause all three phase transmission lines to be opened with an additional negative impact on the utility equipment and dynamic stability of the power system. Thus, a system for reclosing faulted transmission lines immediately after the secondary arc is self-extinguished is needed.